Catherine J.

asked • 05/10/17

5(2u+6)-12u

how do I simplify this?

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Kenneth S. answered • 05/10/17

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I really do not like the answer provided earlier by Marthe.  Her claim that "You're factoring to get u" is incorrect.
Her advice "Now, set it all to zero to solve for u" is completely off base!
 
The student gave an EXPRESSION, not an equation, not a function.
 
It can be simplified by applying the distributive law and collecting LIKE terms:
 
5(2u+6)-12u  = 10u +30 -12u  =  -2u +30.
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Marthe T.

I wrote "set it to zero TO SOLVE FOR u." If they weren't asked to and don't have to, they would simply leave it off and still have your final answer considering I said, "...simplifying from there would mean grouping like terms and THEN ADDING LIKE TERMS," arriving at "-2u + 30" that you wrote & I just chose not to give. I didn't assume the question was issued to them exactly as posed here, and even then, there's still nothing incorrect about my answer. They wouldn't lose any points, but whatever gets you going. 
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05/10/17

Kenneth S.

Marthe:
Do not read more into a question than is there, when the question is straightforward and limited.
Do not mis-use the word factoring, as you did.
Do not SOLVE (set to zero) when that is NOT requested. What was requested was SIMPLIFICATION.
 
DO try to answer exactly the question that is posed. You should not confuse the student by implying that other things are ASSUMED to be necessary.
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05/10/17

Marthe T. answered • 05/10/17

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You're factoring to get u. This could read as f(u)=5(2u+6)-12u as well.
Expand the equation to distribute the parentheses and get rid of it: remember a(b+c)=ab+ac  ? 
5(2u+6) = [2u x 5] + [6 x 5] = 10u + 30
Leaving us with,  10u + 30 - 12u
 
Simplifying from there would mean grouping like terms then adding like terms.
Now, set it all to zero to solve for u. 
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